Tunable capacitors have various uses in RF systems including as voltage-tunable devices. Some benefits of tunable capacitors are integration of different values and functions of capacitance. Applications for tunable capacitors can include tunable filters, voltage controlled oscillators, tunable phase shifters, tunable matching networks, low-impedance power supplies, decoupling high-frequency signals at an IC bonding pad, or others.
Integrated circuits including tunable capacitors can, for example, be used in portable electronics for low-power wireless communication (e.g., cellular phones, pagers, PDAs, and so forth), directional antenna systems, high clock-rate microphones, miniature DC to DC converters, or other devices.
Conventional coplanar tunable capacitors are not easily used in consumer electronics because the spacing of the RF electrodes typically requires a very high tuning voltage to attain the electric field across the gap to realize any useful tuning range for the capacitor. These voltages, up to 100V or 200V cannot be easily generated in mobile equipment and low-cost applications.